The broad band laser emission observed from organic dye lasers provides a source of continuously tunable coherent radiation. Dye laser tuning was first accomplished in 1967 by Soffer and McFarland by replacing the back reflector of the optical resonant cavity with a rotatable diffraction grating. Since that time other organic dye laser tuning techniques for producing narrow band laser emission have been devised, most of which have been electro-mechanical in design.
The disadvantages in using any tuning system that has moving parts, such as a rotatable diffraction grating or electro-mechanical devices, is its inherent limitation of operational tuning rate. The present invention is a tuning system having no moving parts. That is, tuning is accomplished by employing stationary components. Another such tuning system employs an accousto-optical cell and a diffraction grating, and an optional angle multiplier. It is disclosed by a present inventor, Richard Swart Hughes, in U.S. Pat. Application Ser. No. 374,476, entitled "Accousto-Optical Deflector Tuned Organic Dye Laser", filed June 28, 1973, which disclosure is included herein by reference. Therein the laser beam deflection is responsive to the radio frequency applied to the accousto-optical cell, and the light frequency reflected back into the system by the stationary diffraction grating is dependent on the angle of incidence of the diffracted beam onto the grating.
The present invention is tunable by employing an electro-optic beam deflection cell and a diffraction grating, and an optional angle multiplier. Beam deflection is responsive to the electrical field applied to the electro-optic crystal. The cell of the present invention has first and second crystalline wedges having separate indexes of refraction when subjected to the same electrical field, and are in contact diagonally of the laser beam such that each increment of the beam's cross-section is subjected to a differential change in index of refraction as the beam is transmitted through the cell. By employing electro-optics the tuning rate of the present invention is many times faster than that of the mechanical and the acousto-optic systems.